Three point hitch systems have been used for many years to couple ground working implements such as plows and harrows to the back of farm tractors for tilling or otherwise working farm land. These hitch systems generally comprise a pair of spaced elongated bars known as draft links that are pivotally mounted to the lower portion of the tractor frame and extend rearwardly therefrom to distal ends. An upper link is also mounted to the tractor frame and extends to a distal end that is disposed above and between the distal ends of the lower draft links. The distal ends of the draft links and the distal end of the upper link are usually provided with manual or semiautomatic latch mechanisms adapted to receive and be securely latched onto the three corresponding latch pins or tow bars of an implement to be coupled to the tractor; thus the name "three point hitch".
One or more selectively extendable and retractable hydraulic rams are generally coupled between the tractor frame and one or both of the draft lengths or between the frame and the upper link. With such an arrangement and with an implement coupled to the hitch and latched in place, the ram or rams can be actuated to raise the hitch system (and thus the implement coupled thereto) for transport of the implement to a remote location, and to lower the hitch system and implement for working the ground.
In the past, a number of latch mechanisms have been developed for coupling farm implements to a tractor's three point hitch system. Examples of such latch mechanisms are illustrated in U.S. Pat. Nos. 2,869,654 of Hershman; 4,549,744 of Herr et al; 4,135,731 of Lorenz et al; 3,065,977 of Virtue et al; and 3,116,075 of Hershman et al. While devices such as those illustrated in these patents have generally represented improvements over purely manual latching means such as removable pins, they nevertheless have exhibited various problems and shortcomings inherent in their own respective designs. Most, for example, require for proper latching or unlatching that the tractor operator dismount the tractor at some stage in the coupling process and manipulate portions of the assembly manually.
In some cases, such as with the device of U.S. Pat. No. 2,869,654, coupling an implement to the tractor requires the operator to back the tractor up to an implement, align the latches of the hitch with the latch pins of the implement, dismount the tractor, couple the upper link latch manually to the upper latch pin of the implement, remount the tractor, and raise the hitch system while pulling the tractor forward to engage the latches of the lower draft links. Obviously, this is a tedious and time consuming process that is inefficient and can be very wasteful, particularly in situations where implements must be changed frequently. Other prior art latch mechanisms also exhibit various degrees of difficulty and generally require some level of manual intervention for proper operation.
Consequently, a continuing and heretofore unaddressed need exists for a latch mechanism usable with a tractor's three point hitch system to couple and latch securely and automatically to the corresponding latch pins of a ground working implement without requiring the operator of the tractor to dismount the tractor and intervene manually. Further, such a latch mechanism should be quickly and easily detachable from the implement when desired, again without requiring the operator to dismount his tractor. It is to the provision of a latch mechanism that exhibits these and other advantages that the present invention is primarily directed.